Hi I have a couple of windows systems that I wanted to install RAID 1 onto, I have purchased PCI express controller cards and extra drives, but here I made a mistake, one PC has an existing 3.5" 160Gb SATA drive, and by mistake I bought a 2.5" 160Gb SATA to pair with this disk.
Does anyone know if this will work? or will the different disk sizes cause an issue with the RAID any comments will be much appreciated.
It will work normally. But it is preferred that your disks as similar as possible.
RAID-1 will work, but you will only be able to make a RAID volume up to the size of the smallest drive (or probably slightly smaller).
In practice, it's generally worth making RAID volumes slightly smaller than the drive itself. I had one issue where I had to replace a Fujitsu MAU3147NP with a MAX3147NP and the MAX3147 was slightly too small to add to the RAID group. I had to back up and rebuild the entire array.